Contributor since 2006, but contributing less and less
I use Wikipedia since 2004 and began contributing in 2006.
I got local accounts on different Wikimedia projects. In 2009 I have renamed my local account on fr.wikipedia.org but not on other Wikimedia projects. I was contributing more and more projects but using using a username a bit different (using a upper case H instead of a lower case h). Moreover I got one contribution from wikitravel.com migrated to wikivoyage.org. At final my Wikimedia contributions where based on four different usernames.
When mw:Extension:UserMerge will be available on Wikimedia I will request merging all my accounts into my global account.